The present invention relates to an apparatus for tissue treatment, such as cosmetic tissue treatment.
It is known to utilise laser light for tissue treatment, such as cosmetic tissue treatment, such as dermal ablation, removal of hair, photocoagulation of veins, etc.
During dermal ablation, a laser ablates a thin epidermal layer of illuminated derma of a patient. During healing, a new epidermal layer is formed on the ablated surface having the look of the derma of a young person; i.e. the new epidermal layer is formed without previously existing scars, wrinkles, etc.
Lasers that operate at a wavelength that is absorbed in water are used for dermal ablation. When the laser power density (W/mm2) at illuminated cells is sufficient, cellular water is superheated causing small explosions that disrupt heated cells.
During photocoagulation of veins, such as spider veins or spider nevi, regions along the vein are subject to selective photothermolys is. The vein is cut off and the pigment, usually blood, is eventually reabsorbed by the body of the patient.
Hair removal is effected by directing a laser beam at a hair follicle to destroy the hair follicle and its adjacent blood vessels by the heat produced by photothermolysis.
During treatment of tissue, such as an epidermal layer, hair, veins, etc, it is essential not to damage underlying or surrounding tissue. Residual heat may cause untreated cells to char and become necrotic, whereby scars may be formed. Thus, it is desirable to apply laser power only to tissue to be treated and only for a short time, to minimise transmission of conducted heat to underlying and surrounding tissue.
To some extend this has been obtained by selective photothermolysis, i.e. laser light is utilised having a wavelength that is selectively absorbed by tissue to be treated and that is not absorbed by the surrounding and healthy tissue. The selective absorption of the laser light causes selective photothermolysis in the tissue to be treated.
It is also known to automatically control whether or not light is transmitted towards tissue of a certain type. In U.S. Pat. No. 5,531,740, an apparatus is disclosed for automatically delivering a laser beam to an intricated coloured region of a treatment area, e.g. for laser photocoagulation treatment of malformed veins. Typically, venular malformation forms an extremely intricate pattern and consequently, the task of precisely delivering the laser beam exclusively to the malformed veins becomes quite formidable. During scanning over the treatment region, the colour of tissue to be treated is detected and the laser automatically treats only areas having a specified colour.
It is a disadvantage of the apparatus that it is bulky and cannot easily be moved into treatment positions in relation to various surfaces of a human body. Rather, a tissue surface to be treated has to be brought into a specific position in relation to the apparatus before treatment can take place.
It is still another disadvantage of the known apparatuses that the distance between the surface to be treated and the output laser beam optics is unknown so that the degree of focusing of the laser beam on the surface to be treated is dependent on the operator.
It is yet another disadvantage of known apparatuses that no feedback on the quality of the treatment currently in progress is provided.
It is therefore desired to accurately control the amount of light energy transferred to tissue to be treated. The amount of energy must be sufficient for the treated cells to photothermolyse, i.e. decompose because of heat generated by light absorption, and, simultaneously, the amount of residual energy heating untreated cells must be so low that untreated cells will not be damaged.
It is an object of the present invention to provide an apparatus for tissue treatment in which one or more tissue parameters are detected and comprising a display for displaying tissue features based on the detected tissue parameters.
It is another object of the present invention to provide an apparatus for tissue treatment, comprising user interface means for selecting areas of tissue for treatment based on the displayed tissue features.
It is yet another object of the present invention to provide an apparatus for tissue treatment in which parameters of the laser beam is automatically adjusted according to one or more detected tissue parameters. This may facilitate different treatment of different tissue features in a single operation.
It is a further object of the present invention to provide an apparatus for tissue treatment that include means for detecting the distance between the surface of tissue to be treated and the output optics focusing treating light onto the tissue so that optimum focusing conditions may automatically be obtained during treatment.
It is still another object of the present invention to provide an apparatus for tissue treatment that includes a temperature measuring device for measurement of tissue temperature.
It is yet still another object of the present invention to provide an apparatus for tissue treatment that is adapted to automatically and accurately treat tissue to a desired depth causing only a minimum of damage to surrounding tissue that are not treated.
According to the present invention, the above-mentioned and other objects are fulfilled by an apparatus for tissue treatment, comprising a light source for emission of a light beam towards tissue to be treated, a handpiece with an output for emission of the treating light beam, a detector means for detection of at least one tissue parameter, and a display for displaying a map of the at least one tissue parameter.
According to another aspect of the present invention, the above-mentioned and other abjects are fulfilled by an apparatus for tissue treatment having a light source for emission of a treating light beam towards tissue to be treated, detector means for detection of tissue temperature and a display f or displaying a map of tissue temperature.
The light beam ma y be emitted from a handpiece.
The handpiece may be adapted to be held in one hand by an operator and may be freely manipulated for easy aiming of the light beam towards various areas of a patient.
It is preferred to shape the handpiece ergonomically so that a comfortable hand grip is provided for the operator of the apparatus. For example, it is preferred to direct the light beam towards a target area at a substantially right angle to the area. The ergonomic form of the handpiece allows the operator to point the light beam at a substantially right angle to the target surface without having to bend the wrist in an uncomfortable way.
Preferably, the handpiece is light so that it is easy for the operator to hold the handpiece and bring it into any desired position in relation to the target surface to be treated. The weight of a preferred handpiece according to the present inventionxe2x80x94interconnecting cables not includedxe2x80x94is less than 500 grams, such as 290 grams, or such as 250 grams.
The handpiece may comprise the light source, such as a laser, such as a solid state laser, e.g. a laser diode.
Alternatively, the apparatus may comprise an optical fibre for transmission of the light beam from the light source to the handpiece. The fibre has a beam-inlet end that is aligned with the emitted light beam so that a light beam is coupled into the optical fibre and a beam-outlet end for emission of the transmitted light beam. The handpiece is coupled to the optical fibre at the beam-outlet end and comprises an output for emission of the light beam towards a target area of tissue to be treated.
It is preferred, that the light source utilised in the present invention is a laser, but other light sources, such as light emitting diodes and halogen bulbs, may be utilised.
The power emitted by the light source utilised is dependent on the specific application of the light source. For example, when removing hairs, a method is disclosed in U.S. Pat. No. 5,925,035, ThermoLase Corporation, wherein a substance, such as a mixture of carbon particles and oil, may be applied to the tissue area to be treated. The substance may then enter the hair duct and light of a wavelength readily absorbed in the substance may illuminate the area to be treated. The power of the light source, preferably a laser, such as a Nd YAG laser, is then chosen so that the carbon particles are heated to a temperature sufficient to devitalise the tissue feeding the hair so that the hair dies.
Another example is the use of the light source to merely activate cells, such as tissue cells, bacteria, or viruses being present in or at the tissue. These cells may be present inherently or they may be applied e.g. for the purpose of Photon Dynamic Therapy, and in most cases the cells to be treated are undesired and the aim of the treatment is to destroy, activate, damage or in any other way affect the cells to obtain a desired treatment of these cells.
Alternatively, the light source may be any laser capable of emitting light with sufficient power for illuminated cells to decompose, such as CO2 lasers, YAG lasers, such as Erbium YAG lasers, Holmium YAG lasers, Nd YAG lasers, etc., semiconductor lasers, pulsed lasers, gas lasers, solid state lasers, Hg lasers, excimer lasers, etc.
Thus, the laser may be used for ablating a thin epidermal layer of the derma of a patient, removing marks on the tissue, such as marks from chloasma, liver spots, red spots, tattoos, blood vessels just below the surface, etc, as well as warts, wounds, hair follicles, etc.
Present CO2 lasers emit light at a wavelength of 10600 nm. The CO2 laser is particularly well suited as a light source in an apparatus for ablating dermal cells as water has a high energy absorbance at 10600 nm and the CO2 laser is capable of reliably delivering the required laser power.
Erbium YAG lasers emit light at a wavelength of 2930 nm. Water absorbs less energy at this wavelength than at 10600 nm. Therefore, the Erbium YAG laser may be preferred for ablating thinner layers of dermal cells than may be ablated with a CO2 laser. Tissue having been treated with light emitted from an Erbium YAG laser may heal faster than tissue having been treated with CO2 laser light as a thinner layer of dermal cells is influenced by Erbium YAG laser light. An Erbium YAG laser may also be preferred when photocoagulation of blood vessels should be avoided.
A CO laser emits light in the 4500 nm to 5500 nm wavelength range. Water absorption at these wavelengths is somewhat less than water absorption at 10600 nm. A CO laser light source is presently preferred for dental treatment, e.g. for removal of carries, as dentine is not influenced by illumination of light from a CO laser.
A Nd YAG laser with a frequency doubled output beam in the 520-680 nm wavelength range is presently preferred as a light source for treatment of hypervasculation. Light in this wavelength range causes photocoagulation of blood without affecting surrounding tissue provided that an appropriate intensity of the light beam is directed towards the microvessels for an appropriate period of time. Coagulation stops blood flow in the treated vessels whereby discoloration of the skin also stops.
Cellular water absorbs light energy, and applying light energy to the cells is therefore an efficient way of ablating tissue. Thus, for tissue ablation, it is preferred to use light sources, such as lasers, generating light at wavelengths with a high absorption in water, preferably wavelengths larger than 190 nm, such as wavelengths in the range from 190 nm to 1900 nm, preferably from 700 nm to 900 nm, and even more preferred approximately 810 nm, or, preferably wavelengths larger than 1900 nm, such as wavelengths in the range from 1900 nm to 3000 nm, preferably from 1900 nm to 2200 nm, preferably from 1900 nm to 2100 nm, or, from 2800 nm to 3000 nm, and even more preferred approximately 2930 nm, or wavelengths equal to or greater than 4500 nm, such as wavelengths in the range from 4500 nm to 11000 nm, preferably from 4500 nm to 5500 nm, alternatively from 10000 nm to 11000 nm, such as around 10600 nm.
Typically, a power density greater than about 50 W/mm2, such as a power density in the range from about 50 W/mm2 to about 180 W/mm2, is adequate for vaporising cells with a minimum of damage to the surrounding tissue.
However, when removing hairs, the wavelength of the light is preferred to be approx. 810 nm. At this wavelength the absorption of the light in the hair follicles is lower than at higher wavelengths, and the energy density must therefore be higher than 50 J/cm2, preferable not higher than 150 J/cm2, preferably approximately 100 J/cm2. The pulse width may vary from 50 ms and to several seconds. In one preferred embodiment of the invention a pulse width of 50-100 ms, such as approx. 100 ms, is used. But also longer pulse widths, such as pulse widths of 50 ms-3 seconds, such as 50-500 ms, or such as 100 ms-1 second, such as approx. 250 ms, approx. 500 ms, or such as approx. 1 second, may be used.
Generally, the power density and/or the energy density is adapted to the wavelength applied and the tissue to be treated.
The optical fibre for interconnection of the light source with the handpiece according to an embodiment of the present invention may be any fibre, such as a polycrystalline silver halide fibre for transmission of infrared light, etc, that is suitable for transmission of light emitted from the light source and that is made of a material that allows repeated bending of the fibre, so that the handpiece can be freely manipulated for easy aiming of the light beam towards various areas of a patient. It is of course envisaged that the fibre used is adapted to the applied light source. For the interconnection of a light source emitting light in the visible wavelength range or near infrared range it is preferred to use a quartz fibre doped according to the specific wavelength range.
Tissue or tissue features may be classified into specific tissue types according to predetermined values of various parameters, such as colour, temperature, texture, elasticity, size, shape, etc.
For example, various tissue features, such as marks on the tissue, such as marks from chloasma, liver spots, red spots, tattoos, blood vessels just below the surface, etc, as well as warts, wounds, hair follicles, etc, may be detected by their colour. Thus, the detector means may comprise light detectors for detection of intensity of light emitted from tissue at the target area, the target area being the area to be treated by the light beam or being the area the handpiece is currently directed at.
Further, certain types of tissue, such as small marks on the tissue such as marks from chloasma, liver spots, red spots, tattoos, blood vessels, beauty spots, freckles, etc, to be treated are characterised by the shape or the size of the area covered by the type of tissue in question. For example, when treating different types of marks of substantially identical colours it may be desirable to treat each type of mark differently and according to the respective size or shape of the type of mark in question.
The light detector is preferably a semiconductor light detector, such as a photodiode, etc.
The light detector may be positioned inside the handpiece.
The target area may be illuminated by an illuminating light source, such as a white light source, and the reflected light from the target area may be detected by the detector means and analysed so as to characterise the type of tissue that is illuminated.
Further, illuminating light sources emitting light of different predetermined wavelengths towards the target area may be provided. For example, the illuminating light sources may comprise two light emitting diodes, one for emission of light in the wavelength range where the light is considered red and the other for emission of light in the wavelength range where the light is considered green. Also the illuminating light sources may comprise three, four or even more light emitting diodes for emission of light of different wavelength ranges. The light sources may alternatively emit light in the ultra violet or infrared wavelength range. Light from the light sources is transmitted towards the target area and is reflected by tissue at the target area. The reflected light is detected by the detector means and the intensity of reflected light in the two or more wavelength ranges in question characterises one or more parameters of tissue that is illuminated.
The illuminating light source or light sources illuminating the target area may be positioned inside the handpiece.
The apparatus for tissue treatment may comprise an infrared detector, such as an infrared photo detector, for detection of intensity of infrared light emitted from tissue at the target surface, e.g. for determination of the temperature of the tissue. Like colour, temperature may be utilised for characterisation of tissue features. Further, tissue temperature may be utilised for monitoring of treatment progress and quality. The temperature of treated tissue increases during treatment and measurement of tissue temperature may be utilised for verification of the effect of the treatment. For example, when a specific tissue temperature is reached within a specific area, treatment of that tissue may be terminated, e.g. further treatment may be inhibited, as sufficient treatment has already been accomplished. Further, if a certain temperature has not been reached during treatment, output power of the light source may be increased to increase efficiency of the treatment.
The infrared detector may be positioned in the handpiece.
The apparatus is adapted to display a map of tissue features of an area of tissue on a display unit, such as a CRT, an LCD, a TFT display, etc. Tissue features may be characterised by specific values of certain parameters, such as colour, temperature, thickness, texture, elasticity, size, and shape, etc, or by values of mathematical functions of such parameters.
Tissue features may be displayed as graphical three dimensional plots showing surface profiles of selected mathematical functions of tissue parameters of the mapped area.
Alternatively, tissue features may be displayed as a colour map, i.e. predetermined ranges of values of a selected mathematical function of tissue parameters are allocated selected colours to be displayed in areas of the map mapping tissue areas with the respective function values.
Further, the functions may include averages, weighted averages, correlations, cross-correlations, etc, of mathematical functions.
The display unit may be positioned on the handpiece.
The apparatus may further comprise user interface means for selection of specific tissue areas for treatment based on the displayed tissue map. For example, the display unit may comprise a touch screen for displaying the tissue map and an operator of the apparatus may select a tissue area for treatment by touching the corresponding area on the touch screen.
Alternatively, the user interface means may conventionally comprise moving a pointer on the display unit for pinpointing tissue areas to be treated, such as means for moving, such as a mouse, a track ball or a roller key, such as a roller corresponding to the smart Navi Roller from Nokia.
For example, beauty spots may be distinguished from surrounding tissue by their colour. Thus, the displayed map may show the tissue area in natural colours, e.g. as recorded by a video camera, such as a CCD camera. The operator of the apparatus may then, in any conventional manner, select the beauty spots to be removed, such as by moving a pointer on the display unit around a beauty spot thereby selecting the surrounded area for treatment, or, the apparatus may comprise image processing software detecting and marking areas with a beauty spot that will be treated if selected by the operator, e.g. by touching the marked area to be treated.
Likewise, the displayed map may show the temperature of a mapped tissue area, e.g. by displaying specific temperature ranges in specific colours. The temperature map may be used to verify the result of a treatment of the tissue. Areas with temperatures within certain temperature ranges may be selected by the operator as previously described for further treatment.
Further, several maps may be displayed simultaneously on the display unit, e.g. utilising overlay techniques. For example, a map of tissue showing the tissue in natural colours may be overlaid by a temperature map whereby temperatures of certain tissue features, e.g. temperatures of beauty spots after treatment, are indicated to the operator.
The handpiece may comprise deflection means for adjustable deflection of the light beam emitted towards tissue to be treated.
When the handpiece is kept in a fixed position in relation to a target surface which is illuminated by the light beam, changing of the position of the deflection means causes the light beam to traverse or scan the target surface along a path or a curve. An area may be traversed or scanned by the light beam, e.g. by letting the light beam traverse or scan a meander like path substantially covering the area or, by traversing or scanning the area line by line. In the present context, the type, number and shape of paths traversed by the light beam in order to traverse a specific area is denoted the traversing pattern or the scan pattern. The area that is scanned or traversed by the light beam is denoted the scan area, the treatment area or the traversed area. The light beam may treat the surface at the target area and the light beam is therefore also denoted the treating light beam.
The deflection means may comprise any optical component or components suitable for deflecting light of the wavelength in question, such as mirrors, prisms, diffractive optical elements, such as holograms, grids, gratings, etc, etc.
Further, the handpiece may comprise the deflection means.
The deflection means are preferably adjustably mounted for displacement of the deflection means as a function of time, so that the light beam may traverse a surface along a predetermined path, while the apparatus is kept in a fixed position. Preferably, the deflection means are rotatably mounted, and the actual deflection of the light beam is determined by the current angular position of the deflection means. This is a particular advantage when the handpiece comprises the deflection means as the handpiece then may be kept in a fixed position during scanning of the surface target area whereby scanning of the surface is not depending on operator skills. Moving means may be utilised to control positions of the deflection and focusing means, such as actuators, such as piezo electric crystals, the displacement of which is controlled by applying a specific electric voltage to their electrodes, electromotors generating linear or rotational displacements, galvanometers, magnetically activated or controlled actuators, pneumatic actuators, hydraulic actuators, etc.
The positions of the deflection means may be controlled by deflection control means adapted to control the deflection means to deflect the light beam in such a way that it traverses a target surface along a predetermined path.
According to an embodiment of the invention, an apparatus is provided, having two mirrors that are rotatably mounted in the path of the light beam in the apparatus. The rotational axis of the mirrors may be substantially perpendicular to each other in order to obtain two dimensional deflection of the light beam. Further, a handpiece may be provided having the two mirrors rotatably mounted in the path of the light beam in the handpiece.
Alternatively, the deflection means may comprise one mirror that is rotatable around two axes that may be substantially perpendicular to each other.
The mirrors may be connected to electromotors for angular positioning of the mirrors, e.g. each mirror may be directly connected to a corresponding shaft of a motor, whereby each motor is used for angular positioning of the corresponding mirror.
In order to minimise the size of the handpiece, it is preferred to mount the motors with their respective shafts in a common plane. For example, one motor may be a linear motor, such as a linear step motor, generating linear displacements. The shaft of this motor may be connected to the mirror at a first edge of the mirror, while a second and opposite edge of the mirror is rotatably connected to the handpiece. By pushing or pulling the first edge by the linear motor, the mirror is rotated about its rotational axis. The other motor, preferably a galvanometer, may be connected to the other mirror in the conventional way described above, whereby the two mirrors may be rotated around substantially perpendicular axes.
The deflection control means may be adapted to control the deflection means so that the predetermined path is a substantially straight line.
Preferably, the deflection control means are adapted to control the deflection means so that the light beam traverses a target surface area line by line.
It is an important advantage of the line by line scan pattern that areas of any arbitrary shape, such as polygonal, such as rectangular, quadratic, triangular, etc, or circular, elliptic, etc, may be traversed line by line by appropriately controlling the starting point and stopping point of light emission along each line traversed.
Preferably, the first deflection control means are adapted to control the first deflection means so that the lines are traversed sequentially i.e. neighbouring lines are traversed successively without interleaving. Thus, neighbouring lines are traversed within a very short time period so that time will be insufficient for involuntary hand movements of the operator to move the handpiece back to the line previously scanned which would lead to uneven treatment of the target surface. Thus, the requirement for the operator to be able to keep the handpiece steady in a desired position is hereby minimised.
In interlaced scanning every second line of the target surface area is scanned successively and after that the remaining lines in-between are successively scanned. Thus, there would be sufficient time between scanning of neighbouring lines to allow involuntary movements of the operator to move the handpiece back to a line previously scanned. Hereby, some areas may be subjected to repeated treatment whereby tissue may be damaged while other areas may be left without treatment.
Preferably, the first deflection control means is adapted to control the first deflection means so that the lines are scanned in the same direction. Thereby, substantially the same amount of power per area is delivered uniformly across the target surface area leading to substantially the same temperature increase at any point of the target surface area after scanning.
When a target area is traversed line by line, it is preferred that movement of one mirror causes the light beam to traverse a line while movement of the other mirror moves the light beam to the next line. In the example above, the galvanometer preferably generates the line scanning as the galvanometer can move the mirror at a high speed, and the linear motor preferably generates the displacement of the light beam to the next line to be traversed.
As mentioned earlier, when cells are to be ablated it is preferred to control the amount of energy delivered to the cells to be ablated, as the amount of energy must be sufficient for the dermal cells to vaporise and, simultaneously, the amount of residual energy heating non-ablated cells must be so low that non-ablated cells will not be seriously damaged. Thus, when an area of tissue is traversed, e.g. line by line, it is preferred that neighbouring lines substantially abut each other. Clinical investigations have shown that, typically, an overlap of 0.1 to 0.2 mm is acceptable, and a distance between traversed lines of up to 0.1-0.2 mm is acceptable.
In order to control positioning of paths on the target area this accurately, it is preferred to position the deflection means extremely accurately e.g. in the handpiece. In the preferred embodiment of the invention, this is accomplished by utilisation of printed circuit technology providing high accuracy of hole positioning of 0.05 mm. The mirrors are rotated around shafts that are mounted in printed circuit boards providing the required positioning accuracy. Further, the motors rotating the mirrors are also mounted on the printed circuit boards providing electrical connections to the motors and the mechanical support and positioning needed.
When scanning a target surface area line by line, it is for applications, such as ablation of tissue or destruction of bacteria or viruses, preferred to traverse each line in the same direction ensuring uniform heating of cells across the target surface area. Further, it is preferred to turn off the light beam, e.g. by switching off the light source, by inserting a light obstructing member in the light path of the beam, etc, while the light beam is moved from the end of a line having been traversed to the start of the next line to be traversed, in order to avoid repeated illumination of areas of the two lines. It is thus preferred that the lines are abutting each other and not overlapping.
Instead of turning the light source off, the light beam may be moved at a speed significantly larger than the scanning speed, during movement from the end of a line to the start of the next line.
In other applications, for example when the objective of the treatment is removal of hairs, it is preferred to scan the target surface area by a light beam illuminating a spot size at the target area being larger than the spot size usually applied by ablation of tissue, the spot size applied ranging from 1 to 9 mm, preferably from 2 to 8 mm, more preferred from 2 to 6 mm, or most preferred the spot size is approximately 3 mm. When removing hairs, it is preferred to scan the tissue along a curve in steps whereby the illuminated spot is allowed to stay in a specific treating position 60-100 ms, preferably approximately 80 ms, followed by movement of the spot to the next treating position within a few milliseconds. Preferably, the distance between two succeeding treating spot positions is less than a spot diameter, such as approximately half a spot diameter, such as between half a spot diameter and a diameter of the spot, so as to provide for a controlled overlap of the spots resulting in an effective hair removal. The thus implied overlap ensures a uniform distribution of energy across the traversed tissue area, and thus a uniform removal of hairs. It is further preferred to scan the tissue area along a meander curve constituted by lines scanned successively in opposite directions having a spot overlap such as mentioned above.
Typically, the intensity within the beam of a light beam as generated by the light source varies as a normal function of the distance from the centre of the beam. The optical fibre may be designed or selected to be dispersive in such a way that the intensity function of the light beam emitted from the fibre as a function of the distance to the centre of the beam is substantially rectangular, i.e. the intensity of the beam leaving the fibre decays more slowly towards the edge of the beam than the intensity of a beam as generated by the light source whereby heat is more uniformly generated in cells across a traversed line of tissue.
However, when using large spot sizes, such as the spot sizes used when removing hair, the intensity function of the light beam emitted from the fibre is not substantially rectangular, whereby a spot overlap as mentioned above is necessary to obtain a uniform distribution of heat.
The apparatus may further comprise light beam control means comprising outputs for controlling various parameters of the light beam emitted by the light source, such as wavelength, output power, duty cycle, active time, pulse width, inter pulse delay, etc. Based on mathematical functions of tissue parameters as measured by the detector means, the light beam control means adjusts corresponding parameters of the emitted light beam. For example, when two illuminating light sources are utilised for detection of tissue parameters as previously described, predetermined reflected light intensity value ranges for the two wavelength ranges may be stored in a memory of the light beam control means. During treatment, measured values of reflected light intensity are compared with the stored predetermined ranges and when measured values are within the stored ranges treatment is enabled and otherwise it is disabled.
Treatment may be disabled by stopping the emission of the light beam by shutting off the light source or by inserting a shutter in the path of the light beam. Alternatively, the parameters of the light source emitting the light beam may be controlled (e.g. by lowering the output power of the light source) so that tissue at the target area is not influenced by the light beam.
Further, the wavelength and/or the power of the light beam emitted by the light source may be adjusted according to the measured values. For example, a plurality of predetermined ranges of reflected light intensity may be stored in the memory and during treatment the measured values may be compared to the stored ranges and the value of the wavelength and/or the power of the light beam may be set according to relations between measured values and stored ranges. Alternatively, the light beam control means may calculate and control the wavelength and/or the power of the light beam as a predetermined function of measured values of reflected light.
The output power of the light beam may be adjusted by adjustment of the continuous output power of the light source, by adjustment of the duty cycle of the light source, etc.
The detector means may be utilised for detection of various tissue parameters during scanning of the light beam across a tissue area so that treatment and tissue parameter determination are performed substantially simultaneously including automatical adjustment of light beam parameters according to detected tissue parameter values.
Current values of light beam parameters may be displayed on the display unit together with the tissue map.
The user interface means may comprise means for modifying one or more of the automatically adjusted light beam parameters.
The apparatus may be adapted to continuously update the tissue map during treatment so that actual tissue parameters are displayed in real time whereby the operator can follow the effects of the treatment in real time, which will allow the operator to modify light beam parameters during treatment in response to the displayed results of the treatment.
The apparatus may further comprise tissue parameter storage means, such as an EEPROM, a flash EEPROM, a hard disk, etc., for storage of coherent data sets of signal values provided by the detector means at positions along the path traversed by the treating light beam during treatment and the corresponding positions themselves thereby mapping tissue parameters as a function of stored relative positions along the path. Further, the light beam control means may be adapted for controlling parameters of the light beam during a second movement of the light beam along the above-mentioned predetermined path in accordance with the coherent data sets stored.
For example, without automatic control of tissue treatment, removal of hair, removal of callosities, such as Millner spots or other small spots which are easily discriminated from the surrounding tissue, is a difficult task to perform as a large number of small spots having diameters of 100 Πm-3 mm, such as 200 Πm-2 mm, such as 500 Πm-1.5 mm, such as approximately 0.5 mm, such as approximately 1 mm, have to be pinpointed by the operator performing the treatment. According to the present invention, the apparatus scans the surface tissue area with hair to be removed without treatment. Hereby the hair follicles are detected by colour determinations as described above and their positions along the scanned path of the light beam are stored in the tissue parameter storage means and the corresponding tissue map is displayed on the display. The operator then selects specific areas of the map for treatment or selects treatment of the entire scanned area. Treatment light beam parameters may be displayed and the operator may choose to adjust the light beam parameters proposed by the apparatus. During a second scan of the tissue area and within the tissue areas selected for treatment, the light beam is turned on and off according to the content of the tissue parameter storage means and the selected light beam parameters so that solely the hair follicles detected during the first scan and positioned within areas selected for treatment are treated preventing the surrounding tissue from being damaged. Alternatively, the parameters of the light beam are automatically adjusted according to the content of the tissue parameter storage means so that when the light beam impedes on a hair follicle within an area selected for treatment, the power-per-area of the light beam is adjusted so that the detected hair follicles are destroyed and when the light beam impedes on tissue without a hair follicle the power-per-area of the light beam is reduced so that this surrounding tissue is not damaged. The user interface means comprising the display may be positioned on the housing of the handpiece.
The parameters may comprise scanning velocity of the treating light beam from the handpiece, intensity of the treating light beam emitted form the handpiece, size of the target surface area to be scanned by the treating light beam, shape of the target surface area to be scanned by the output light beam, etc.
The user interface means may comprise a first button, such as a membrane switch, a touch key on the display, etc, for selection of a parameter type by stepping through a set of parameter types, such as the set listed above or any subset thereof.
The user interface means may further comprise a second button for selection of a parameter value of the parameter type currently selected by stepping through a corresponding set of parameter values. Preferably, the parameter values are displayed on the display. Alternatively or concurrently, a set of light emitting diodes may be provided for indication of the set of currently selected parameter values.
It is an important advantage of provision of the user interface comprising the display at the handpiece that an operator of the handpiece is able to simultaneously select operational parameters of the handpiece and observe resulting changes in treatment effects since the operator is not forced to shift his field of view from the surface area to be treated to a user interface panel positioned somewhere else, e.g. behind the operator.
Preferably, the buttons are positioned on the housing of the handpiece so that single-handed operation is possible, preferably, with the right as well as with the left hand.
The user interface means may further comprise a foot pedal. The light beam traverses a target surface area when the operator depresses the pedal. Preferably, light beam scanning is stopped immediately when the operator releases the pedal and the emission of the light beam towards the target surface area is prevented.
Furthermore, a cooling fluid, such as water, such as a gel, etc. may be applied to the surface to be treated during treatment. For example, the fluid may be applied between two plates of a material transparent to the light beams to be used during treatment. The fluid may be positioned in a substantially closed reservoir between the two plates or the reservoir maybe provided with an in-let and an out-let whereby the fluid may pass through the reservoir to ensure constant cooling during treatment.
Thus, the apparatus may comprise a cooling member that is adapted to be positioned at the target area for cooling of tissue at the target area and that is at least partly transparent to the light beam. The cooling member may comprise a frame, an upper window positioned in the frame, and a lower window positioned in the frame, the frame, the upper window, and the lower window defining a volume therebetween for receiving and holding a cooling liquid. Further, the cooling member may comprise an inlet for inputting cooling liquid to the volume and an outlet for outputting cooling liquid from the volume. The cooling member may be attached to the handpiece.
To obtain an optimum result of treatment, it is important to keep the light beam focused at the target area during treatment.
The apparatus may comprise means for automatically controlling the distance from the apparatus to the focus point in such a way that the light beam is automatically focused at the target area during treatment. For example, if the handpiece comprises the means for automatically controlling, the distance from the handpiece to the focus point is controlled.
Thus, the detector means may comprise a detector array and array optics for forming an image of the target area on the array. Further, the detector means may comprise image processing means for processing output signals from the detector array.
Preferably, the image processing means is adapted to calculate the size of a spot on the target area illuminated by the light beam, or another light source of the apparatus, and imaged onto the detector array.
The apparatus may further comprise output optics for focusing the light beam onto the surface of tissue to be treated and movably positioned at the output of the apparatus for adjustment of the distance between the apparatus and the focus point, and focus control means for adjusting the position of the output optics in response to the value of the calculated spot size.
For example, the handpiece may comprise the output optics for focusing the light beam onto the surface of tissue to be treated whereby the distance between the handpiece and the focus point is adjusted by adjusting the position of the output optics in response to the value of the calculated spot size.
According to another embodiment of the invention, two crossing visible light beams are emitted from the handpiece, the cross point of the beams indicating the focus point of the treating beam. The image processing means are adapted to detect the number of spots imaged onto the detector array, and the focus control means are adapted to adjust the position of the output optics in response to the number of spots and, preferably, the distance between them (if more than one).
Alternatively, a number of light beams may be emitted from the handpiece, the light beams forming a cone of light, the diameter of the cone at the tissue surface indicating the focus point of the treating light beam.
In a preferred embodiment of the invention, the light beam control means further comprises switching means for preventing emission of the light beam and being controlled by the light beam control means so that emission of the light beam is prevented during a detecting scan from a predetermined first position to a predetermined second position along a predetermined path. During the detection scan the detector means detect light reflected from the target surface area along the predetermined path and the reflected light is analysed by the detector means or alternatively the reflected light is analysed by a microprocessor common to the control means of the apparatus.
By pulse width modulating the light source, energy delivered to the target surface may be varied along a traversed line in addition to the variations created by adjustment of parameters of the light beam in response to detected tissue parameters. A fade-in area may be created by starting scanning of each traversed line with short pulses of light between longer periods of no light. As the line is traversed, the duration of the light pulses may be increased while the periods with no light may be decreased. Outside the fade-in area, the light beam may not be pulsed whereby the remaining part of each line is traversed with a constant intensity of the light beam.
Likewise, a fade-out area may be created by after having traversed a part of a line with constant light intensity, pulse width modulating the light source to transmit shorter and shorter pulses of light towards the line at the target surface area ending with no light transmitted at the end of the line.
The maximum amount of energy delivered by the light beam to the target area is determined by the fade-in or fade-out function and can not be exceeded by the adjustment of parameters of the light beam. However, the adjustment may result in a amount of energy delivered that is lower than the maximum amount of energy.
The fade-in or fade-out scanning patterns may also be created by gradually increasing or decreasing, respectively, the power of the light source, or by decreasing or increasing, respectively, the scanning speed of the light beam.
Alternatively, a combination of these methods may be used.
The shape of the traversed area including the fading area may for example be polygonal, such as rectangular, quadratic, triangular, etc, circular, elliptic, etc.
A traversed line with fade-in and/or fade-out provides a smooth transition from a non-ablated area of tissue to an ablated area of tissue. This is a particularly advantageous feature when the apparatus according to the present invention is used for treatment of small marks on the tissue such as marks from chloasma, liver spots, red spots, tattoos, blood vessels etc.
Light intensity control means may be provided for generating a control signal for transmission to a light source interconnected with the optical fibre and controlling intensity of light emitted by the light source and transmitted through the optical fibre.
The fade-in and fade-out may be provided by controlling the intensity of the light beam and/or the velocity of the scanning light beam along a predetermined path and the light intensity control means and/or the deflection control means may be adapted to provide fade-in and fade-out.
The light intensity control means and/or the deflection control means may be adapted to control the intensity of the light beam and/or the velocity of the scanning light beam along a predetermined path as a function of the position of the light beam inside the area of the target surface area.
To provide the normal ablation of tissue, the light intensity control means may be adapted to provide a substantially constant intensity of the light beam and the deflection control means may be adapted to provide a substantially constant velocity of the scanning light beam when the scanning light beam is inside a first part of the target surface area.
If desired, the fade-in and fade-out effect may be provided either by scanning the light beam with a velocity larger than the substantially constant scan velocity within the treatment area of tissue or, by decreasing the output power of the light beam.
The light beam control means may be adapted to control the power-per-area of the light beam when scanned along a predetermined path on a target tissue area to be treated. For example, when ablating tissue it is presently preferred to maintain the power-per-area of the light beam inside a first part of the target tissue area at a substantially constant level.
In order to create the fade-in or fade-out effect, the power-per-area of the light beam when outside a first part of the target tissue area may depend on the distance to the first part of the target tissue area, and it is preferred that the power-per-area of the light beam increases with decreasing distance to the first part of the target tissue area.
Keeping the intensity of the light beam substantially at the constant level as provided inside the first part of the target tissue, fade-in and fade-out may be provided by scanning the light beam with a velocity larger than the substantially constant scanning velocity within the first part of the target tissue area.
Likewise, keeping the velocity of the scanning light beam substantially constant inside the first part of the target tissue, the fade-in and fade-out may be provided by emitting a light beam with a smaller intensity than the substantially constant intensity of light emitted within the first part of the target tissue area.
The light intensity control means and/or the deflection control means may be adapted to provide a varying intensity of the light beam outside the first part of the target surface area. The intensity of the light beam may be varied between a first intensity being substantially identical to the substantially constant intensity in the first part of the target tissue area and a second intensity being an intensity at substantially zero, i.e. no light is emitted from the output of the handpiece or the second intensity may be a low intensity not affecting tissue.
The user interface means may also enable selection of parameters relating to fade-in and fade-out, such as scanning velocity of the output light beam from the apparatus, e.g. the handpiece, in the fade-in or the fade-out area, intensity of the output light beam emitted from the apparatus in the fade-in or the fade-out area, size of fade-in or fade-out areas, shape of fade-in or fade-out areas, etc.
In the case where the light beam is invisible, e.g. utilising an infra red emitter, an ultra violet emitter, etc, a light source generating visible light may be provided for generating a visible light beam that is used to assist the operator by indicating areas towards which the invisible and treating light is directed during scanning. For example, the input connector of the handpiece may be further adapted to connect a second beam-outlet end of a second optical fibre for transmission of a visible light beam to the handpiece. The second optical fibre is preferably properly aligned in the connector in relation to the predetermined path of the visible light. The handpiece may further comprise second deflection means for adjustable deflection of the visible light beam in such a way that the light beam and the visible light beams emitted from the output of the handpiece illuminate substantially the same area of a target surface.
Further, two crossing visible light beams may be emitted from the apparatus or the handpiece, the cross point of the beams indicating the focus point of the light beam. Alternatively, a number of light beams may be emitted from the handpiece, the light beams forming a cone of light, the diameter of the cone at the tissue surface indicating the focus point of the treating light beam.
Preferably, common deflection means are utilised for deflection of all light beams emitted from the apparatus or the handpiece whereby tracking of the light beams are easily accomplished. The deflection means may thus comprise Zinc selenide lenses, as they are transparent for visible light as well as for infrared light.
In order to further assist the operator of the apparatus, the visible light beam may, e.g. between scanning with the light beam, be traversed around at least a part of the circumference of the target surface area thereby indicating the size, shape and position of the target surface area to be traversed with the light beam.
When a polygonal shape of the target surface area has been selected, the visible light beam may, e.g. between scans by the treating beam, be scanned along one edge of the polygon.
Thus, the method may further comprise the step of transmitting a visible light beam towards the target surface area utilising the first deflection means.
The method may further comprise the step of scanning the visible light beam along at least a part of the circumference of the target surface area to be traversed by the light beam.
In order to further assist the operator of the apparatus in keeping a constant distance from the output of the handpiece to the surface of the tissue to be ablated, the handpiece may comprise a distance member connected to the handpiece at the output with fastening means.
As the distance member will touch the patient, it is desirable to insert a new, disinfected member before treatment of a new patient and thus, it is preferred that the fastening means comprises a magnet so that a used distance member can easily be disconnected from the handpiece, e.g. for autoclaving, and so that a new member can easily be connected to the handpiece.
The apparatus according to the present invention may further comprise a processor for control of the apparatus and comprising one or more control means, such as deflection control means, light beam control means, light intensity control means, etc. The processor may further be connected to the user interface means and may be adapted to control the functions of the handpiece in accordance with inputs from the user interface means.
According to a preferred embodiment of the invention the processor means is positioned inside the handpiece.
The processor may comprise a memory, such as an EEPROM, such a flash EEPROM, such as hard disk, etc., for storing of different parameters of scanning patterns and fade-in and fade-out patterns, such as target surface area size, scanning duration, etc. Further the processor means may comprise the tissue parameter storage means for storage of coherent data sets of signal values provided by the detector means at positions along the predetermined path and the respective corresponding positions thereby mapping tissue parameters as a function of stored relative positions along the path.
The apparatus, e.g. in the form of a handpiece may further be provided with a computer interface facilitating reception of scanning pattern parameters generated in a computer and transmitted to the apparatus for storage in the memory. The user interface may be utilised for selection of a specific scan pattern from the set of patterns stored in the memory as previously described. The computer may be any programmable electronic device capable of storing, retrieving and processing data, such as a PC.
It is an important advantage of provision of a processor in the handpiece that signal lines between the handpiece and an external device controlling the handpiece are not needed. This reduces weight of the handpiece with cables connected. Further, electrical noise on control lines is minimised because of reduced lengths of the lines. Still further, control speed is increased as capacitance of a short line is small.
Various scan patterns may be created on a PC and be downloaded to the memory of the handpiece. The patterns may be stored in the form of a table of parameters defining number of lines, length of lines, distance between lines, start and end points of fade-in and fade-out of each line, points of turn on and turn off of the scanning light beam, etc of each scan pattern stored.
A scan pattern box may be provided, containing a processor, a memory and interface means for storage of scan patterns generated, e.g. on a PC and transmitted to the box through the interface means for storage in the memory. The interface means of the box and the computer interface of a handpiece may be interconnected and the various scan patterns stored in the box may be transferred to the memory of the handpiece whereby scan patterns created at a single PC may be distributed to a plurality of handpieces that may be situated remotely from the PC.